Electric switch



June 1, 1954 Filed May 23 1951 R. K. SHEWMON ELECTRIC SWITCH 2Sheets-Sheet l nii-CMQ@ H16 ATTQQNEYS June 1, T9521 R. K. sHEwMoN m57ELECTRIC SWITCH Filed May 23 1951 2 Sheets-Sheet 2 aL/M42 `r-- V V43JNVENTOR.

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Patented June 1, 1954 ELECTRIC SWITCH Ralph K. Shewmon, Dayton,

General Motors Corporation, corporation of Delaware Ohio, assignor toDetroit, Mich., a

Application May 23, 1951, Serial No. 227,815

4 Claims. l

Thisv invention relates toV an electric switch.

It' is among the objects of the present invention to provide an`electric switchV in which the cooperating contacts are held inengagement with a constant or even an increasing pressure up to theinstant said contacts are disengaged with a snap action.

A further object of the present invention is to provide an electricswitch with means` tending substantially to increase contact engagementpressure up to the instant said contacts are disengaged even thoughsaidswitch is actuated very slowlyor in a hesitating manner as would bethe case where the switch is actuated by a thermoresponsive, or by afioat controlled means.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to theaccompanyingdrawings, wherein a preferred embodiment ofr thepresentinvention is clearly shown.

In the drawings:

Fig. l illustrates anV electric motor driven sump pump equipped with thepresent invention.

Fig. 2 is a side view of the switch at actual size;

Fig. 3 isy a cross sectional View taken along the line and in thedirection of the arrows 3*-3 oiy Fig. 7.

Fig. 4 is a cross sectional view, at enlarged scale; taken along theline and in the direction ofthe arrows 41-4 of Fig. 2.

Fig. 5A is a perspective View of the cam actuating lever;

Fig. 6 is a view partly in section and partly in elevation showingcooperating switch parts-in contact closing positions;

Fig. 7 is a View similar to Fig. 6, showing the cooperating switch partsin an intermediate p'osition.

Fig. 8 is a similar View showing the switch vparts in the contact openposition.

The switch of the present invention is particularly adapted for use inconnection with electrically driven devices in which the switch actuatormoves very slowly and oittimes in a hesitant manner. For instance in aninstallation when the switch is actuated by a thermal responsiveelementy changing temperatures may cause the thermal element tofluctuateA at the pointv at which it should actuate the switch and, as aresult the switch is fluctuated so that its engaging contacts, thoughnot completely separated, are not held together with the proper contactpressure and thereby arcing and pitting of thev contacts results. Thesame is ofttimes true when the switch is actuated by the float member ofa sump pump which, due to fluctuating fiuid levels does not decisivelymove the switch but on the contrary may hesitatingly move it back andforth near the point of switching, thus causing' the contacts to flutterand burn.

The present switch is designed and constructed to have full or evenincreased contact engagement pressure applied until the instant ofthrowover or switching. No mattei' if the switch actuator isvacillatingly moved or oscillated in a uttering manner near the point ofthrow-over or switching, full contact pressure is maintained until, inresponse to one of said fluttering movements, the actuator reaches thezero point at which throw over is attained, causing the contacts to besuddenly disengaged.

Fig. 1 illustratesan installation equipped with the present invention.Here an electric motor 29 drives a sump pump 2l. A iioat 22 is slidablysupported on a rod 23 provided with high level stop 2t and low levelstop 25 engageable by the float. Rod 23 is connected with the actuator29 of the switch to carried by the motor 2o for controlling it. When theoat strikes stop 24 the switch actuator 29- is moved to operate switch30 to start the motor. When stop 25 is engaged by the iioat 22V switch3G is operated to stop the motor.

Switch 3i) shown in detail in the remaining gures of the drawingsconsists of a housing 32 which is U-shaped having side walls 33 and 34and one end wall 35, attached to base 35. A pivot pin #it is supportedby side walls 33 and 3d so as to extend across the housing 3i. Midwaybetween the two side walls, pivot pin iii has an annular groove 4|providing a reduced diameter portion about which the smaller end of theegg-shaped opening i2 in cam 43 rotatably fits, the larger diameter ofsaid opening fitting the pin to permit placing oi*l the cam in theannular groove lil. Whereby the cam may oscillate upon the pin but isheld against movement longitudinally thereon and therefore constantlyheld midway between the two parts of the carrier as will be explainedhereinafter.

Cam 53 has its disc-like head portion rotatably supported upon pin 4t.The head portion of the cam has a lancet arch shaped protuberancepresenting two oppositely disposed similar arcuate cam surfaces i5 and46 diverging from an apex edge l extending across the face of the cam.An arm i8 extends from the head portion of the cam at substantiallyright angles to the protuberance 4-t- This arm extends into and throughan opening in the end wall of the wall of the switch actuator lever 29.

As illustrated in Fig. 5, lever 29 has a one arm portion G, U-shaped incrosss-ection and extending through an opening in the housing 32 of theswitch so as to permit attachment of the switch operating means theretoas shown in Fig. 1. At one end and from each side portion of arm thereextends an angular arm substantially at right angles to the arm 50.Angular arm 5l, extending from the one side of arm 55, has an outwardlyextending ear 52 at its outer end which projects into an opening in theone side wall (it of the housing so as to be rotatably supported in saidopening. Likewise arm 53 extending at substantially right angles fromthe other side wall portion of arm 55, has an ear 5 4 rotatablyextending into a similar opening in the side wall 3Q of the housing.Thus the actuator 29 is pivotally supported in the housing 32, the arms5l and 53 of said actuator each being at a respective side of thecarrier to be described. Each arm portion El and 53 has an enlargedopening 55 through which the pivot pin lil extends, said openingspermitting oscillation of the actuator about its pivots 52 and 54without striking the pin.

Housing 32 has a cover G of insulating material which carries two spacedterminals iii and 62 forming the stationary contacts of the switch.These two stationary contacts 6| and 62 are adapted to be engaged andbridged by the movable member '63 provided with a contact element ateach end. Bridging member $3 is spring loaded and movably supported uponthe carrier t5 made of two identical pieces of insulating material t5and @l shown attached one to the other by rivets tc and both pivotallycarried by the pin lit. The carrier has two arm portions 'iii and 'ilextending from a central hub portion l2 substantially at right angles toeach other. The

hub portion 'i2 has a transverse opening which fits over pin ill wherebythe carrier is rotatably supported on said pin and between the two armportions 5I and 53 0f the actuator 29, see Fig. 3. The contactingsurfaces of the two pieces G13 and El of insulating material forming thecarrier are recessed longitudinally of their arm portions lll and "H,said recesses, when the two pieces 65 and i are riveted together,forming an interior chamber in each arm portion extending from near theouter end of the arm toward the pivotal support in the hub portion 'l2where they converge and join. The interior chamber in arm 'lil of thecarrier is designated by the numeral 8B and the corresponding chamber inarm 'lil by the numeral tl. Each arm has a transverse opening passingcompletely therethrough, the one in arm 'ill being designated S2 and inarm ll being designated 33.

As shown in Fig. 4, the bridging member S3 extends through thetransverse opening B3 and is urged toward the side of opening 83adjacent the stationary contacts til- 62 (see Fig. 8) by a spring 35which is in chamber 8i laterally thereof. A nubbin 86 in the bridgingmember winding of its contact carrying ends, is surrounded by the end ofspring 8-5 so that the self adjusting, tiltable bridging member isprevented from accidental removal from the carrier and will align itselfwith the stationary contacts iii- 52 and assure solid contact engagementwhen shifted by the carrier to bridge said contacts.

The chamber 8i! in arm portion 'l0 of the carrier has a ball 9i]contained therein, which is constantly urged into engagement with thecam #it by spring 9 i, the cam, as shown in Fig. 3, being locatedbetween the hub portions l2 of the two pieces 55 and 6l which, whenriveted together, form the carrier t5. rIhe cam is so positionedrelatively to the chamber 8E in the carrier that the lancet arch shapedportion 45-116-4'! is always exposed to the said chamber 8U andtherefore to engagement by the ball 8U in said chamber, said ball beingurged against said cam portion by the spring 9 i.

Figs. i and 6 show the switch mechanism in contact engagement position.Here the bridging element SS is held in engagement with stationarycontacts Si and 62 by spring S5 inasmuch as the carrier 55 is being heldin its extreme clockwise position as regards Fig. 6, by the ball 9Dbeing urged against thearched surface 45 of cam 43 by spring 9 i. Theball engaged surface `45 of the cam being on the clockwise side of theradial line passing from the pivotal center ci cam 43 through the apexline ll'i of the diverging arch like surfaces t5 and lili, the force oispring 9i holding the ball on surface i5 acts against the carrier tourge it clockwise .and thus urge its arm portion 'H toward thestationary contacts and against the cover til, providing a positivestop. 'I'he bridging member t3 engages the stationary contacts 5l-t2before the carrier engages the cover and thus as the carrier continuesits movement to engage the positive stop or cover $30 under the elect ofspring 9 i, the bridging member S3 moves relatively to the carrier andcompresses its spring 35 which now acts to urge the bridging member intoengagement with both stationary contacts 6i and 52.

Assuming that the switch 3B is applied in an installation including amotor driven sump pump as shown in Fig. l, and the dropping water levellowers the floatl 22, as soon as the iioat strikes the stop 2li it willmove the rod 23, connected to the switch actuator lever 2t, downwardlycausing the lever 29 to be moved clockwise about its pivotal ears 52 and5ft supported in the housing of the switch. This movement of the float22 downwardly may be very slow or even hesitant, depending upon thevarying water level and thus movements of the switch lever 29 would bethe same. As the actuator lever 2.9 is moved clockwise about its pivotalears 52 and Ee, the cam 43 connected to said device will likewise berotated clockwise about the pivot pin d so that the arch like surface i5of cam 553 will be moved relatively to the ball et to cause said ball toascend said arch like surface i5 toward the apex line 41. This force ofcam surace i5 against the ball tends to move the carrier clockwise withthe cam and thus said carrier is maintained against the top or cover G9acting as a stop thereby permitting the spring fully to perform itsfunction of urging the bridging member into good engagement with thestationary contacts El-GZ even while the switch is being operated towardits contact breaking position by clockwise operation of the actuatorlever 29 and its connected cam 43. Thus no matter if this lever movementis slow or even hesitant with a tendency to vacillate, contact pressureremains constant and is not; reduced until the instant of completecontact separation.

Fig. '7 shows the relative positions of switch parts at the start ofcontact separation movements. The actuator lever 2Q having been movedclockwise sufciently to rotate cam 63 so that the ball 9B has ascendedthe arch shaped cam surface i5 to reach the apex line 4l, spring 9| willnow urge the ballv Se to descendalong the arch like surface d6 of thecam. Now the ball 90 is on the counterclockwise side of the line 3-3 ofFig. 7 and the spring 9| reacts to shiftthe carrier 55 counterclockwiseabout its pivotal support 40 thereby quickly shifting the bridgingelement 63 from engagement with the stationary contacts (I-82 andbreaking the circuit. This counterclockwise thrust of the carrier E byspring 9| is limited by the striking of the carrier upon the base 36 ofthe switch.

As soon as rising water level raises the oat 22 to strike stop 24 on rod23, the switch actuator lever 29 will again be actuated counterclockwisecausing the cam 43' to be rotated counterclockwise. Now the ball 90ascends the arch like surface 46 of the cam 43 and as soon as the apexline 41 is reached spring SI will urge ball 90 to descend arch likesurface 45, reaction of the spring 9| upon the carrier 65 quicklythrusting the carrier clockwise about its pivotal support 4B and therebycausing the bridging member 53 of the carrier arm 'il to engage andbridge the stationary contacts Gl and G2 to close the motor circuit.

The present invention thus provides a positively acting, quick break,over center switch in which full Contact pressure is assured until theinstant of throw over. This avoids fiuttering and weak Contactengagement thereby eliminating frying or arcing of the contacts anunsatisfactory condition found in most electrical switches andparticularly those actuated by a slowly moving or even hesitatinglymoving actuating member such as a thermoresponsive element or a float ina sump pump.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

l. An electric switch comprising in combination', a pivoted membertiltable in either direction between two positive stops and comprisingtwo angularly disposed arms and having means for pivoting of the same atthe juncture of the said arms; a shaft pivotally supporting said member;a spring loaded ball in one of said arms of said pivoted member;stationary contacts at one of said stops; a spring loaded contactmovably supported by the other of said arms of said member andengageable with the stationary contacts when said pivoted member istilted to engage the stop supporting the stationary contacts; a campivotally supported on said shaft, said cam having substantiallycorresponding diverging surfaces operable within said pivoted member andengageable by the ball and cooperating therewith to effect tilting ofthe pivoted member in one direction or the other dependent upon thesurface engaged by the ball; and actuating means operatively connectedwith the cam for rotating it on said shaft and relatively to the balland pivoted member.

2. An electric switch comprising in combination, a pivoted membertiltable in either direction between two positive stops and comprisingtwo angularly disposed arms and having means for pivoting of the same atthe juncture of the said arms; a shaft pivotally supporting said member;stationary contacts insulatingly carried at one of said positive stops;a contact supporting blade extending through one arm of the pivotedmember so as to be movable with and relative thereto and engageable withthe stationary contacts;

spring means positioned within said one arm and engaging said blade toprovide for resilient movement thereof relative to said blade andprovide pressure holding said blade contacts against said stationarycontacts, a cam pivoted on said shaft so as to be coaxial of the pivotedmember and within the same, said cam having substantially correspondingsurfaces diverging oppositely from a common apex; a ball and a springwithin the other arm of the pivoted member, said spring acting in a line`constantly bisecting the cam supporting shaft for urging the ball intoengagement with the cam portion having the diverging surfaces andconsequently tilting the pivoted member in one direction or the otherdependent upon which diverging surface of the cam the ball is ridingupon; and an actuator operably connected with the cam.

3. An electric switch comprising in combination, a housing insulatinglysupporting stationary contacts; a shaft in said housing; a memberpivotally supported on said shaft within the housing and oscillatablebetween two positions; a contact element carried by said member andmovable thereby into engagement with the stationary contacts in responseto oscillation of said member into one of its positions; a ball in saidinember urged by a spring toward the pivotal support of said members;oscillatable means pivoted on said shaft and engaged by the ball, saidmeans being operative for one portion of its movement in eitherdirection to move the ball and compress its engaging spring whereby thepivoted member is urged into its assumed position at increasing pressureuntil said ball reaches a predetermined point of engagement with saidmeans at which times the spring pressed ball effects sudden movement ofthe pivoted member toward its other position; and an actuator pivoted inthe housing on one side of the said shaft and connected to said means onthe opposite side of the shaft for oscillating said means.

4. An electric switch comprising in combination, a housing; twostationary contacts insulatingly supported in said housing; a pivot pinin said housing; a member of insulating material oscillatably supportedby said pivot pin, said inember having two arm portions extendingradially therefrom, substantially at right angles one to the other, saidmember 1seing movable between two stationary parts of the housing; aspring loaded contact element mcvably carried by one of said armportions and engageable with the stationary contacts when said arm ismoved toward said contacts; a ball and an engaging spring in the otherarm of said member, said spring yieldably urging the ball toward theaxis of the pivot pin; an oscillatable cam pivotally supported by saidpin so as to be coaxial of said member, said cam extending into saidother arm of the oscillatable member and engaged by the ball, theportion of the cam engaged by the ball being lancet arch shapedpresenting two surfaces diverging from an apex, each surface actingeither as a raising or a lowering element for the ball, dependent uponthe direction of cam rotation, whereby said ball, as it ascends a camsurface, compresses the spring yieldably to urge and maintain theoscillatable member in its assumed position with increased pressureuntil the instant said ball reaches the apex of the cam surfaces atwhich time the ball descends along the opposite cam surface and, underthe influence of the spring, quickly thrusts the oscillatable memberinto its other position;

and an actuator lever pvoted in the housing and connected to the cam foroscillating it.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,182,087 Hart May 9, 1916 1,839,095 Goetz Dec. 29, 19311,851,384 Fitzgerald Mar. 29, 1932 10 Number FOREIGN PATENTS CountryDate Great Britain Mar. 1, 1934 Great Britain Dec, 19, 1935 France Nov.28, 1928 France Oct. 24, 1932

